Introduction..... Symbols..... Momentum Notes..... Stationary Plates..... Moving Plates..... Vanes..... Pipe walls.....

IntroductionThe study of forces resulting from the impact of fluid jets and when fluids are diverted round pipe bends involves the application of newtons second law in the form of F = m.a. The forces are determined by calculating the change of momentum of the flowing fluids. In nature these forces manifest themselves in the form of wind forces, and the impact forces of the sea on the harbour walls. The operation of hydro-kinetic machines such as turbines depends on forces developed through changing the momentum of flowing fluids. I have created a excelcalcs spreadsheet for convenient access to all of the equations found on this page . This is located at ExcelCalcs.com calculation Fluid Jets Symbols
Momentum
Newtons Second Law can be stated as: The force acting on a body
in a fixed direction is equal to rate of increase of momentum of the body
in that direction. Force and momentum are vector quantities so the direction
is important. A fluid is essentially a collection of particles and the net force, in a fixed direction,
on a defined quantity of fluid equals the total rate of momentum of that fluid quantity
in that direction. The figure below illustrates this principle at two locations. In its simplest form, with steady flow conditions, the force on a fluid flow in a set direction is equal to its mass flow rate times by the change in velocity in the set direction. The fluid flow also exerts an equal and opposite reaction force as a result of this change in momentum. Jet Forces on Stationary Plates
Considering only forces in a horizontal direction u
Considering only forces Normal to plate surface u
Considering only forces in a horizontal direction u
Considering only forces in a horizontal direction
u
u Jet Forces on Moving Plates......Fluid Machines - Pelton Wheel
Considering only forces in a horizontal direction
Considering only forces in a horizontal direction Jet Forces on Vanes...... Additional notes can be found on webpages
In the x Direction: u The notes below related to vanes as used in impulse turbines. These turbines
derive the mechanical energy mainly from the change in momentum as the fluid passes through the vanes. The conditions as shown when
the vectorial sum of V
In the x Direction The notes below related to the force on a pipe wall resulting from the changes in fluid pressure and fluid momentum as the fluid flows round a pipe bend . Gravity and friction effects are not considered. The fluid is assumed to be flowing under steady state conditions. In the x Direction
The resultant reaction force on the pipe = F |

- The Momentum equation...Useful lecture notes
- Eulers equation for fluid flow .. One page derivation from basic principles
- Turbines .. Notes on turbines explaining the difference between impulse and reaction types